Ecochemical effects of phonolite rock powder, dolomite and potassium sulfate in a spruce stand on an acidified glacial loam

In a field experiment, the ecochemical effects of soil amelioration with dolomite, phonolite rock powder and fertilization with potassium sulfate were compared. By dolomite and phonolite the acid-neutralizing capacity of the soil and the pH level should be stabilized. In addition, the correction of a latent potassium deficiency in spruce stands at acidified glacial loams was intended. In comparison to fertilizing with potassium sulfate liming as well as the application of phonolite rock powder showed a prominent improvement of the soil chemical status already within the first 4-5 years. Both treatments increased the base saturation, the dolomite to a depth of 60 cm, the phonolite to a depth of 30 cm. At the limed plot, strong nitrate leaching occurred with peaks at 80 cm soil depth higher than the EU threshold for drinking water. In the phonolite plot this also occurred, but the nitrate concentrations remained lower. The silicate rock powder reacted more slowly than dolomite. Thus, we can state that silicate rock powder can be an alternative to conventional liming in regions where the risk of nitrate mobilization is high and especially at water preservation areas where special care has to be observed. But the phonolite which was used in this experiment released a considerable amount of sodium, which disturbed the amelioration effect. In practice, it would be better to use a silicate rock powder with a low sodium content. Fertilization with potassium sulfate provided a fast nutritional effect but displayed no potential for soil chemical amelioration.